Python-3.4.3/C2/Subplots/English-timed

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Time Narration
00:01 Hello friends! Welcome to the spoken tutorial on Subplots.
00:06 At the end of this tutorial, you will be able to create and switch between subplots.
00:14 To record this tutorial, I am using:

Ubuntu Linux 14.04 operating system,

Python 3.4.3,

IPython 5.1.0.

00:29 To practise this tutorial, you should know how to:

run basic Python commands on the ipython console,

use Plots interactively,

embellish a plot.

If not, see the pre-requisite Python tutorials on this website.

00:48 Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously.

Now, type ipython3 and press Enter.

01:01 Let us initialise the pylab package. Type: percentage pylab and press Enter.
01:10 To compare two plots, we draw the plots in the same plotting area.
01:15 Let us now create two plots- a cosine plot and an exponential curve in the same plotting area.
01:24 Type: x equals to linspace inside brackets 0 comma 50 comma 500 and press Enter.

plot inside the brackets x comma cos(x).

01:45 Type: y equals to linspace inside brackets 0 comma 5 comma 100.

plot inside brackets y comma y square.

02:04 Here, the two plots have different regular axes. So, we cannot draw overlaid plots.
02:13 In such cases, we can draw subplots.
02:17 We use 'subplot' command to accomplish this.

Type: clf()

subplot inside the brackets 2 comma 1 comma 1.

02:33 We can see the first subplot. The subplot command takes three arguments.
02:40 The first argument is the number of rows of subplots that must be created.

Here the first argument is 2 to split the plot horizontally.

02:53 The second argument is the number of columns of subplots that must be created.

Here, the second argument is 1. So, plot will not split vertically.

03:07 The last argument specifies the serial number for the subplot.

Here, we passed 1 as the argument which creates the upper subplot.

03:19 If we execute the subplot command as-

subplot inside the brackets 2 comma 1 comma 2, the lower subplot is created.

03:34 Here, we can see now two subplots.
03:38 Now, we can draw plots in each of the subplot area using the plot command.

Type: subplot inside brackets 2 comma 1 comma 1.

plot inside brackets x comma cos(x).

04:00 Now, type: subplot inside brackets 2 comma 1 comma 2

plot y comma y square

04:16 This created two plots, one in each of the subplot area. The top subplot holds a cosine curve and the bottom subplot holds a parabola.
04:29 It is clear from the two subplots that both have different regular axes.
04:35 For the cosine curve, x-axis varies from 0 to 50 and y-axis varies from minus 1 to 1.
04:46 For the parabolic curve, x-axis varies from 0 to 5 and y-axis varies from 0 to 25.
04:57 Now clear the plot window.
05:00 Pause the video. Try this exercise and then resume the video.
05:05 Pressure, Volume and Temperatures are held by the equation Pv equals to nRT where nR is a constant.
05:16 Assume nR equals to 0.01 Joules per Kelvin and T equals to 200K. V can be in the range from 21cc to 100cc.
05:29 Draw two different plots as subplots:

Pressure v/s Volume plot and

Pressure v/s Temperature plot.

05:39 Switch to the terminal for the solution.
05:43 To start with, we have been given the range of Volume from which we can define the variable v.
05:51 v equals to linspace inside brackets 21 comma 100 comma 500.
06:03 We can create first subplot and draw Pressure v/s Volume graph using this v.

subplot(2 comma 1 comma 1)

plot(v comma 2 point 0 by v)

06:24 We know that nRT is a constant which is equal to 2.0

since nR is equal to 0.01 Joules per Kelvin and T equals to 200 Kelvin.

06:38 Now, we can create the second subplot and draw the Pressure v/s Temperature plot as follows.

subplot(2 comma 1 comma 2)

plot(200 comma 2 point 0 divided by v)

07:02 We have an error now, telling x and y dimensions don't match.
07:08 So, we will create same number of points for temperature.
07:14 Type: t equals to linspace inside brackets 200 comma 200 comma 500.
07:27 Now, we have 500 values in t and each with the value 200 Kelvin.
07:35 Plotting this data, we get the required plot.

plot inside brackets t comma 2 point 0 divided by v

07:48 We can see two subplots of Pressure v/s Volume and Pressure v/s Temperature respectively.
07:56 This brings us to the end of this tutorial.

In this tutorial, we have learnt to create subplots and to switch between them.

08:08 Here are some self assessment questions for you to solve.
08:12 1. Which of the following is correct?

subplot inside brackets numRows comma numCols comma plotNum ,

subplot inside brackets numRows comma numCols ,

subplot inside brackets numCols comma numRows.

08:36 And the answer is first option.

1.The subplot command takes three arguments namely the number of rows, number of columns and the plot number.

08:48 Please post your timed queries in this forum.
08:53 Please post your general queries on Python in this forum.
08:59 The FOSSEE team coordinates the TBC project.
09:04 Spoken-tutorial is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
09:15 This is Usha from IIT Bombay, signing off. Thank You.

Contributors and Content Editors

Pratik kamble, Sandhya.np14